Syndiotactic propylene polymers and lubricating oils comprising the same

Abstract

This disclosure relates to syndiotactic polymers containing units derived from propylene and units derived from C 4 to C 20 alpha olefins. The polymers can be prepared is slurry or solution polymerization processes using a zirconium-containing metallocene catalyst system. The polymers have a melt flow rate as determined by ASTM D-1238 (230° C., 2.16 kg) of from about 0.1 to about 20 g/10 min. The syndiotactic polymers are useful as viscosity index improvers.

What is claimed is: 
     
       1. A lubricating oil composition comprising:
 (i) at least 50 wt % of a base oil based on the weight of the lubricating oil; and 
 (ii) a syndiotactic polymer containing units derived from at least one α-olefin having 4 to 10 carbon atoms and ≥50 mol % of units derived from propylene, wherein the polymer has a melt flow rate, as determined by ASTM D-1238 (2.16 kg, 230° C.), of about 1 g/10 m to about 10 g/10 min, and wherein the lubricating oil composition comprises about 0.1 wt % to about 10 wt % of the polymer based on the weight of the lubricating oil composition; 
 wherein the polymer is produced by a polymerization process comprising contacting propylene and at least one α-olefin having 4 to 10 carbon atoms with a catalyst system comprising a precatalyst compound and an activator in a reactor; 
 wherein the precatalyst compound is selected from those having the structure of formula (1), (2), (3), or (4); 
 wherein structure (1) has a Cs or pseudo-Cs symmetry and the following formula (1): 
 
       
         
           
           
               
               
           
         
         wherein
 M is a zirconium; 
 L 1  is a unsubstituted fluorenyl, unsubstituted heterocyclopentapentalenyl, unsubstituted heterofluorenyl, substituted fluorenyl, substituted heterocyclopentapentalenyl, or substituted heterofluorenyl ligand with one or more symmetric or pseudo symmetric substituents, each substituent group being, independently, a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl, and optionally two or more adjacent substituents may join to form a substituted or unsubstituted, saturated, partially unsaturated or aromatic, cyclic or polycyclic substituent; 
 L 2  is a cyclopentadienyl ring or a substituted cyclopentadienyl ring with one or more symmetric or pseudo symmetric substituents in the 2 and 5 positions of the ring, each substituent group being, independently, a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl; 
 G is a bridging group; and 
 X are, independently, halogen, alkoxide, aryloxide, amide, phosphide, hydride radicals, hydrocarbyl radicals, substituted hydrocarbyl radicals, halocarbyl radicals, substituted halocarbyl radicals, silylcarbyl radicals, substituted silylcarbyl radicals, germylcarbyl radicals, or substituted germylcarbyl radicals; or both X are joined and bound to the metal atom to form a metallacycle ring containing from 3 to 20 carbon atoms; or both together can be an olefin, diolefin or aryne ligand; or both X can also be joined to form a anionic chelating ligand; 
 wherein structure (2) has Cs or pseudo-Cs symmetry and the following formula (2): 
 
       
       
         
           
           
               
               
           
         
         wherein:
 M, L 1 , G, and X are the same as in structure (1); 
 J is a heteroatom from group 15; 
 R′ is a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, or substituted halocarbyl; and 
 L′ is a neutral Lewis base and w represents the number of L′ bonded to M where w is 0, 1, or 2, and optionally any L′ and any X may be bonded to one another; 
 
         wherein structure (3) has Cs or pseudo-Cs symmetry and the following formula (3): 
       
       
         
           
           
               
               
           
         
         wherein:
 M and X are the same as in structure (1); 
 L 3  is a cyclopentadienyl ring optionally substituted in the 4 position of the ring, the substituent group being chosen from a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl; 
 L 4  is a substituted cyclopentadienyl ring with symmetric or pseudo symmetric substituents in the 3 and 5 positions of the ring, each substituent group being, independently, a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl; and 
 G′ and G″ are bridging groups; and 
 
         wherein structure (4) has C2 symmetry and the following formula (4): 
       
       
         
           
           
               
               
           
         
         wherein:
 X is the same as in structure (1); 
 M is titanium; 
 O is oxygen; 
 N is nitrogen; 
 R 1  is a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl; 
 R 2  is a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl; and 
 RL 3 , R 4  and R 5  are independently hydrogen or a radical group which is a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl. 
 
       
     
     
       2. The lubricating oil composition of  claim 1 , wherein the at least one α-olefin comprises 1-hexene. 
     
     
       3. The lubricating oil composition of  claim 1 , wherein the lubricating oil composition comprises about 0.5 wt % to about 5 wt % of the polymer based on the weight of the lubricating oil composition. 
     
     
       4. The lubricating oil composition of  claim 1 , wherein the base oil is selected from Group II base oil, Group III base oil, Group IV base oil, Group V base oil, and combinations thereof. 
     
     
       5. The lubricating oil composition of  claim 1 , wherein the polymer has a thickening efficiency of greater than 1.5. 
     
     
       6. The lubricating oil composition of  claim 1 , wherein the lubricating oil composition has at least one of: a kinematic viscosity at 40° C., as measured by ASTM D445-3, of greater than 50 cSt, and a kinematic viscosity at 100° C., as measured by ASTM D445-5, of greater than 10 cSt. 
     
     
       7. The lubricating oil composition of  claim 1 , wherein the lubricating oil composition has a viscosity index, as calculated by ASTM D2270, of greater than 120. 
     
     
       8. The lubricating oil composition of  claim 1 , wherein the precatalyst compound has the structure of formula (1) and has Cs or pseudo-Cs symmetry of formula (1a) or (1b);
 wherein structure (1a) has the following formula (1a): 
 
       
         
           
           
               
               
           
         
         wherein each R a  and R b  are selected from hydrogen, halogen, hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl, germylcarbyl or polar radicals, and optionally two or more adjacent substituents may join to form a substituted or unsubstituted, saturated, partially unsaturated or aromatic, cyclic or polycyclic substituent, with the proviso that each R a  is the same and each R b  is the same and allow the compound to be Cs-symmetric or pseudo Cs-symmetric; 
         each R c  is a symmetric or pseudo symmetric substituent with respect to the other and is selected from hydrogen or a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl radicals; and 
         each R d  is a symmetric or pseudo symmetric substituent with respect to the other and is selected from hydrogen or a hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl or germylcarbyl radicals; and 
         wherein structure (1b) has the following formula (1b): 
       
       
         
           
           
               
               
           
         
       
     
     
       9. The lubricating oil composition of  claim 1 , wherein the precatalyst compound has the structure of formula (3) and has Cs or pseudo-Cs symmetry of the following structure (3a): 
       
         
           
           
               
               
           
         
         wherein R e  is selected from hydrogen, hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl, or germylcarbyl radicals; 
         each R f  and R g  are selected from hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, silylcarbyl, or germylcarbyl, with the proviso that each R f  and R g  are chosen to allow the compound to be Cs-symmetric or pseudo Cs-symmetric. 
       
     
     
       10. The lubricating oil composition of  claim 1 , wherein the precatalyst compound comprises di(para-triethylsilylphenyl)methylene(2,7-di-tertbutyl fluorenyl)(cyclopentadienyl)zirconium dimethyl. 
     
     
       11. The lubricating oil composition of  claim 1 , wherein the activator comprises one or more of N,N-dimethylanilinium tetra(pentafluorophenyl)borate, N,N-dialkylphenylanilinium tetra(pentafluorophenyl)borate where the alkyl is a C1 to C18 alkyl group, trityl tetra(pentafluorophenyl)borate, tris(pentafluorophenyl)boron, tri-alkylammonium tetra(pentafluorophenyl)borate where the alkyl is a C1 to C18 alkyl group, tetra-alkylammonium tetra(pentafluorophenyl)borate where the alkyl is a C1 to C18 alkyl group. 
     
     
       12. The lubricating oil composition of  claim 1 , wherein the molecular weight distribution (Mw/Mn) of 1.0 to 2.5. 
     
     
       13. The lubricating oil composition of  claim 1 , wherein the polymer contains at least 60 mol % of units derived from propylene. 
     
     
       14. The lubricating oil composition of  claim 1 , wherein the lubricating oil composition has a kinematic viscosity at 40° C., as measured by ASTM D445-3, of less than 500 cSt. 
     
     
       15. The lubricating oil composition of  claim 1 , wherein the lubricating oil composition has a kinematic viscosity at 100° C., as measured by ASTM D445-5, of less than 50 cSt. 
     
     
       16. The lubricating oil composition of  claim 1 , wherein the lubricating oil composition has a kinematic viscosity at 100° C., as measured by ASTM D445-5, of greater than 10 cSt to less than 40 cSt.